Reduction of indigo coloring-matters.



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ROBERT WIMMER, OF LUDW'ilGSHAFEN-UhiJliHlihiti-lll ilt, tEtlEltl /irtNY,

ASSIGNUR TU BADISGHE ANILIN do .EEQDA lldlttttilth Uh lUUDtVlEGS- liiAlFEN-Ulfii iflihdtldltl lltl, GERMANY, it tlUltlltJltrtTiliQhl.

no. season fipeeification of Letters JPatent.

rates-tea May is, race.

Application filed April 22, 1905- tterial No. 256,986.

To rtZZ whom it may concern.-

- Be it known that I, Bonner WIMMER, a subject ofthe King of Bavaria; residing at Ludwi shafen-oirthe-lthine, in the Kingdone 0? Bavaria, German Empire, have invented new and useiul llmprovements in the in the, presence of caustic-alkali solutions much stronger than have hitherto been eniployed or proposed. 1 have found, for instance, that the reduction proceeds in a caus tic-alkali solution often degrees Baum,

- B.) although more strongly concentrated so lutions may be employed. Uf course the iron used must be in a iinely-livided condition. The reaction commences at a temperature of about fifty degrees centigrade, C.)-

An advantage of my invention is that after the reduction in accordance therewith the solution can be filtered and the filtrate (which contains a high percentage of indigo white) can be placed on the market Without any further treatment, since it contains no metal, Whereas zinc when used as the reducing agent.

' goes into solution and has to be separated be fore the solution can be used for dyeing.

The following examples will serve to fur ther illustrate the nature of my invention, which, however is not coni'med to these examples. -"ll1e parts are by Weight.

Eirampie l: Dissolve one hundred and ten (110) parts of caustic soda in six hundred and forty (MO) parts of water and add sixty parts of iron in a finely-divided state. Heat this to a temperature of seventy-five degrees centigrade (1.) and While stir ring add gradually two hundred and iifty (250) parts of indigo pure B. A. E, which after a short time goes into solution. Filter by the aid of the pump and. wash the residue. in this Way a thirty (30) per cent. solution of indigo White is obtained. Example 2: Add while stirring sixty (60) parts ofil'on-powder to two hundred and fifty (250) parts of caustic-soda solution containing about thirty-five (35) per cent. of NaOl-l, heat to a temperature of about eighty degrees centigrade, Q.) and then add three hundred (300) parts of bromindigo, which becomes reduced after a short time.

Now what i claim is- I The reduction of indigo coloring-matters by heating the same with iron-powder in causticalkali solution-which contains at least six and a hall per cent. of solid caustic alkali.

in testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

. RUBERT WIMMER. Witnesses:

Ennnsr ll. EHRI-IARDT, J. Anne. LLorn. 

